Various types of semiconductor packages include external connector designs which are adaptable to fusion bonding (soldering), socketing or both. One package type which permits a high pin count and surface connection is the gull wing package. In a gull wing package, the leads splay outwardly from the package and can easily be thermally fused to the surface of a printed circuit board. The gull wing package has the advantages of high pin count or pin density, ease of assembly for surface mount applications and ease of inspection for surface mount applications. Unfortunately, it is not ideally suited for socketing.
Often it is desired to provide a semiconductor integrated circuit device part to a circuit board while permitting upgrading by connecting additional semiconductor integrated circuit devices by the user. Typically this is done with semiconductor memory, although processor enhancements and other additional circuitry are added to various circuits. Often such additions utilize common address circuit with the more basic circuit, and the circuit board is capable of addressing the additional semiconductor integrated circuit parts.
By "parts," it is the intent to describe a packaged integrated circuit device, which is provided in a package, which may be plastic or ceramic. The part can be a hybrid integrated circuit, or any other convenient packaged semiconductor integrated circuit part. The term "integrated circuit device" is intended to describe a complete packaged device, as customarily seen in a package such as a gull wing package.
Such additional integrated circuit devices are typically socketed, so that the user need not be skilled at soldering high density parts to accomplish the upgrade. In the past, if an integrated circuit device was originally supplied in a gull wing package, a different package type had to be provided for field upgrades, since the gull wing package was not readily installed subsequent to original assembly of the circuit board.
Circuit layouts also make it convenient to stack integrated circuit devices. If an integrated circuit devices is surface mounted, it is often difficult to further mount a socket over that integrated circuit devices, although the location of that integrated circuit devices presents the desired alignment of the interconnect circuitry for connection of further parts. Placing the integrated circuit devices on the reverse side of the board would be attractive, but parts are often not available in reverse pinout configurations. Therefore a reverse board mounting must accommodate a part installed upside down.
It would be advantageous if a semiconductor part having a high pin count and designed for surface mounting could also be socketed to a board for purposes of end user installation. It would be advantageous to be able to socket such a part in such a way that its pinout alignment matched that of the original, so it would not be necessary to provide a reverse pinout part. It would be advantageous to be able to accomplish stacking of integrated circuit devices parts without limiting the ability to provide a basic configuration of a circuit board with surface mounted integrated circuit devices. In doing so, it would be advantageous if a gull wing semiconductor package could be added to a circuit board after assembly, by socketing the gull wing package to the board.
In addition, in certain types of enhancements, such as increasing memory, it is desired to be able to stack the integrated circuit devices parts. Therefore, if a basic configuration had a memory capacity of x, the end user could add semiconductor integrated circuit devices to increase the capacity by using the same or different capacity integrated circuit devices parts which use the same basic pinout arrangement.